This invention relates to an apparatus for the manufacture of mainly large-diameter flexible hoses having spiralled reinforcement.
It is well known that pressure-tight flexible tubes of various sizes are used increasingly all over the world. The demand for such hoses has sharply increased mainly in the field of exploring crude oil and natural gas and also in the fields of exploitation and transport of same. Demands are increasingly high for hose products having larger sizes, improved pressure resistance and higher quality.
Various machines with different operational principles have been heretofore available. It has always been a most difficult technical problem to uniformly locate the reinforcing threads that are applied so as to provide an improved resistance against pressure and other mechanical effects, while providing uniformity of diameter and thread strength shall also be provided for. Apparatus manufactured for this purpose only have been able to produce flexible tubes having small bores and a low number of reinforcing threads. Hungarian Pat. No. 154,707 discloses that to meet quality requirements the best method is to simultaneously apply the reinforcing threads of each layer onto the flexible tube base. In this way a harmful deformation of the base structure caused by non-uniformity of the reinforcement's diameter can be avoided.
There has been no means available for making large-diameter flexible tubes containing reinforcing plies of thread-layers whereby the building-up of all the reinforcing threads of one layer would be completed simultaneously. However, the use of such method could improve not only the quality of products but also the capacity of the apparatus. The difficulty in solving said problem lies in that hundreds of thread drums would have to be located and the guiding and handling of such a great number of threads are so difficult that in known apparatus only a few threads can be applied onto the surface of the base tube in one step while that process has to be repeated several times. Hungarian Pat. No. 154 707 describes a fibre guiding system where the drums are located over the level of the apparatus. This method provides the best possibility among the methods heretofore known for guiding a higher number of threads when using a fixed guiding system. However, this known method cannot provide for the positioning of, e.g. a thousand bobbins, though this requirement is very often demanded. Because of the difficulties mentioned above, various second-best solutions have been forced to be adopted. According to one of these solutions the base is cured first before applying the reinforcing threads and the several plies of reinforcement required are applied in subsequent steps. Though the disadvantageous deformation of the base can be remarkably reduced, it cannot be fully eliminated. The capacity of this known machine is low because of the repeated thread applying operation. By another method suggested it is proposed to calender parallely guided reinforcing threads into thin rubber sheets. That means that the reinforcement is first located between rubber sheets having a thickness of some mms and the cylindrical surface and the flexible tube is then covered by these reinforced sheets. The application of said known method causes a lot of problems: the sheets containing reinforcement cannot follow, in the case of steel cords, for instance, deviations from the theoretically cylindrical surface of the base structure. Again, in the case of steel cords, the edges of the reinforcement are because of the same reason, either overlapped or there arise gaps between the edges. For the production of steel cords an expensive, separate apparatus which is independent from the hose building-up process is needed.
It is also known that the number of threads cannot be increased economically when fixed thread guiding systems are used because their location may only extend to two dimensions that is, the drums or bobbins can be located in one plane only. Three-dimensional systems cannot be developed at all, or they are limited to certain forms. In the latter the space exploitation factor available is very low because enough access space should be provided for refilling or replacing the drums or bobbins.
The main object of the present invention is to provide an apparatus which is substantially free of the limitations described above.